#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unordered_map>

#define COMMAND_SIZE 1024
#define FORMAT "[%s@%s %s]# "

// 下面是shell定义的全局数据

// 1.命令行参数表
#define MAXARGC 128
char *g_argv[MAXARGC];
int g_argc = 0;

// 2.环境变量表
#define MAX_ENVS 100
char *g_env[MAX_ENVS];
int g_envs = 0;

// 3.别名映射表
std::unordered_map<std::string ,std::string> alias_list;

// for test
char cwd[1024];
char cwdenv[1028];

// last exit code
int lastcode = 0;

const char* GetUserName()
{
	const char* name = getenv("USER");
	return name == NULL ? "None" : name;
}

const char* GetHostName()
{
	const char* hostname = getenv("HOSTNAME");
	return hostname == NULL ? "None" : hostname;
}

const char* GetPwd()
{
	//const char* pwd = getenv("PWD");
	const char* pwd = getcwd(cwd,sizeof(cwd));
	if(pwd != NULL)
	{
  		snprintf(cwdenv, sizeof(cwdenv), "PWD=%s", cwd);
		putenv(cwdenv);
	}
	return pwd == NULL ? "None" : pwd;
}

const char* GetHome()
{
	const char* home = getenv("HOME");
	return home == NULL ? "" : home;
}

void InitEnv()
{
	extern char **environ;
	memset(g_env, 0, sizeof(g_env));
	g_envs = 0;

	//本来要从配置文件来
	// 1.获取环境变量
	for (int i = 0; environ[i]; i++)
	{
		// 1.1申请空间
		g_env[i] = (char*)malloc(strlen(environ[i])+1);
		strcpy(g_env[i], environ[i]);
		g_envs++;
	}
	g_env[g_envs++] = (char*)"HAHA = for_test"; //for test
	g_env[g_envs] = NULL;

	// 2.导成环境变量
	for(int i = 0; g_env[i]; i++)
	{
		putenv(g_env[i]);
	}
	environ = g_env;
}

//command
bool Cd()
{
	// cd argc = 1;
	if(g_argc == 1)
	{
		std::string home = GetHome();
		if(home.empty()) return true;
		chdir(home.c_str());
	}
	else
	{
		std::string where = g_argv[1];
		// cd - / cd ~
		if(where == "-")
		{
			// Todu
		}
		else if(where == "~")
		{
			// Todu
		}
		else
		{
			chdir(where.c_str());
		}
	}
	return true;
}

void Echo()
{
	if(g_argc == 2)
	{
		// echo "hello world"
		// echo $?
		// echo $PATH
		std::string opt = g_argv[1];
		if(opt == "$?")
		{
			std::cout << lastcode << std::endl;
			lastcode = 0;
		}
		else if(opt[0] == '$')
		{
			std::string env_name = opt.substr(1);
			const char *env_value = getenv(env_name.c_str());
			if(env_value)
				std::cout << env_value << std::endl;
		}
		else
		{
			std::cout << opt << std::endl;
		}
	}
}

// / /a/b/c
std::string DirName(const char* pwd)
{
#define SLASH "/"
	std::string dir = pwd;
	if(dir == SLASH)
		return SLASH;
	auto pos = dir.rfind(SLASH);
	if(pos == std::string::npos)
		return "BUG?";
	return dir.substr(pos+1);
}

void MakeCommandLine(char cmd_prompt[],int size)
{
	snprintf(cmd_prompt,size,FORMAT,GetUserName(),GetHostName(),DirName(GetPwd()).c_str());
	//snprintf(cmd_prompt,size,FORMAT,GetUserName(),GetHostName(),GetPwd());
}

void PrintCommandPrompt()
{
	char prompt[COMMAND_SIZE];
	MakeCommandLine(prompt,sizeof(prompt));
	printf("%s",prompt);
	fflush(stdout);
}

bool GetCommandLine(char* out,int size)
{
	// ls -a -l => "ls -a -l\n" 字符串
	char *c = fgets(out,size,stdin);
	if(c == NULL)
		return false;
	out[strlen(out)-1] = 0; // 清理\n
	if(strlen(out)==0)
		return false;
	return true;
}

//3.命令行分析 "ls -a -l" -> "ls" "-a" "-l"
bool CommandParse(char *commandline)
{
#define SEP " "
	g_argc = 0;
	// 命令行分析 "ls -a -l" -> "ls" "-a" "-l"
	g_argv[g_argc++] = strtok(commandline,SEP);
	while((bool)(g_argv[g_argc++] = strtok(nullptr,SEP)));
	
	g_argc--;
	return g_argc > 0 ? true : false;
}

void PrintArgv()
{
	for(int i=0; g_argv[i]; i++)
	{
		printf("argv[%d]->%s\n", i, g_argv[i]);
	}
	printf("argc: %d\n", g_argc);
}

bool CheckAndExecBuiltin()
{
	std::string cmd = g_argv[0];
	if (cmd == "cd")
	{
		Cd();
		return true;
	}
	else if (cmd == "echo")
	{
		Echo();
		return true;
	}
	else if(cmd == "exprot")
	{}
	else if(cmd == "alias")
	{
		// std::string nickname = g_argv[1];
		// alias_list.insert(k, v);
	}

	return false;
}

int Execute()
{
	pid_t id = fork();
	if(id == 0)
	{
		// child
		execvp(g_argv[0], g_argv);
		exit(1);
	}
	int status = 0;

	//father
	//pid_t rid = waitpid(id, nullptr, 0);
	//(void)rid; // rid使用一下
	
	pid_t rid = waitpid(id, &status, 0);
	if(rid > 0)
	{
		lastcode = WEXITSTATUS(status);
	}

	return 0;
}


int main()
{
	// shell 启动的时候, 从系统中获取环境变量
	// 我们的环境变量信息应该从父shell统一来
	InitEnv();

	while(true)
	{
		//1.输出命令行提示符
		PrintCommandPrompt();

		//2.获取用户输入的命令
		char commandline[COMMAND_SIZE];
		if(!GetCommandLine(commandline,sizeof(commandline)))
			continue;

		//3.命令行分析 "ls -a -l" -> "ls" "-a" "-l"
		if(!CommandParse(commandline))
			continue;
		//PrintArgv();

		//4.检测并处理内建命令
		if(CheckAndExecBuiltin())
			continue;

		//5.执行命令
		Execute();
	}
	return 0;
}

